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National Overview

Based on the Palmer Drought Index, severe to extreme drought affected about 8 percent of
the contiguous United States as of the end of April 2008, a
decrease of about 1 percent
compared to last month. By contrast, about 12 percent of the
contiguous U.S. fell in the severely to extremely wet
categories.

Historical temperature, precipitation, and Palmer drought data
from 1895 to present for climate divisions, states, and regions in
the contiguous U.S. are available at the Climate Division:
Temperature-Precipitation-Drought Data page in files having
names that start with "drd964x" and ending with "txt" (without the
quotes).

Detailed Drought Discussion

A shift in the weather
pattern occurred during April, with much of the eastern Great Lakes
and adjoining Northeast having below-normal
precipitation. The dryness, combined with periods of much
warmer-than-normal temperatures, created a spell of short-term
drought in that region. Unusually
dry weather persisted across parts of the northern and southern
Great Plains, the Lower Mississippi Valley, and much of the West,
especially the Southwest. Beneficial
precipitation fell across the Upper Mississippi Valley, the
mid-Atlantic States, and parts of the Southeast. As a result,
drought conditions improved in the Southeast and western Great
Lakes, but deteriorated in the High Plains and Southwest (April 29 USDM
versus April 1
USDM).

Drought conditions in the Southeast continued to improve, with USDM
statistics showing moderate to extreme drought covering about
43% of
the region by the end of April compared to about
59% at the end of last month. However, long-term hydrologic
deficits remained, with low groundwater
and streamflow
levels and several states ranking in the top ten driest category
for May-April.

This month marked the second consecutive dry month for much of the
Southwest. Arizona
and California
had the driest March-April on record. The winter
snowpack has mostly melted out of the extreme Southwest
mountains, filling reservoirs and increasing streamflows in Arizona
which has helped urban areas. But dry and windy weather for the
last 8 weeks has parched rural areas and increased fire danger.
Elsewhere, however, mountain snowpack remained healthy with most of
the intermountain
and Northwest regions reporting above normal snow packs by the
end of the month. Delayed snowmelt and persistent cool weather have
resulted in below-normal streamflow
and reservoir
levels across parts of the Northwest.

The persistent dryness has depleted soil
moisture, especially in the
High Plains but also across parts of the West
and Southeast, and ravaged crop and rangeland, especially in
the southern High Plains. Streamflow (both modeled
and observed)
averaged below normal across the Southeast, Southwest, northern
High Plains, and parts of the Northeast.

A more detailed drought discussion can be found below.

SOUTHEAST DROUGHT

According to the Southeast
Regional Climate Center, April was a rather quiet month, with a
few notable exceptions. There was some rain throughout the region,
although relatively few intense storms and little flooding. Many
stations in the north of the region had above normal rainfall for
the month, with Richmond, VA exceeding its long term average by
over 150%, with a monthly total of 8.32 inches (211 mm). Much of
this fell on the 20th through the 22nd of the month, when an upper
level low brought rain to much of Virginia and eastern North
Carolina. Cape Hatteras, on the Carolina coast, had its third
wettest April since 1895. No major recording stations anywhere in
the region were more than 1 inch (25 mm) below their long-term
average values for the month. During the last 3 months large
portions of the coastal plains of all the states had slightly more
than normal precipitation. But inland areas had less than normal.
Areas west of Charlotte, NC, south of Atlanta, GA and east of
Birmingham, AL all had little more than 50% of their usual
precipitation since the beginning of February.

As a long-term result, and despite the recent rain, the dry
conditions continued through most of the region, with the northern
parts of Alabama and Georgia, along with west-central North
Carolina, still in Extreme Drought. Thus in some regions,
particularly in the north, the reservoirs were full at month's end,
giving a superficial impression that the drought was over. But
ground water levels were still very low, with many wells throughout
the region being several feet below their normal level.

SOUTH REGION DROUGHT

As noted by the Southern
Regional Climate Center, April
monthly precipitation totals varied spatially throughout the
region. The wettest portions of the Southern Region included most
of Arkansas, western Tennessee, and central and northeastern Texas.
Elsewhere in Texas, conditions were quite dry with precipitation
totals ranging from as low as 4% of normal at El Paso and Del Rio,
to approximately 30% near Amarillo and 40% at Houston. In Oklahoma,
April precipitation totals were quite low in the panhandle
(approximately 5-25% of normal). In Louisiana and southern
Mississippi, precipitation totals for the month at most stations
varied from approximately 25 to 50% of normal.

According to the April 29
USDM, drought conditions were observed in five of the six
states within the Southern Region. In Texas, drought has persisted
in the western half of the state and conditions have slightly
deteriorated there from last month. For instance, as of April 29
approximately 45% of the state was experiencing moderate drought
conditions or worse, with approximately 31.8% showing severe
drought conditions or worse. Approximately 10% of the state was
experiencing extreme or exceptional drought. This area was
primarily restricted to the south and south central counties. The
eastern half of the state remained clear of drought conditions. In
Oklahoma, the panhandle was experiencing moderate to severe
drought; however, it covered only an area that makes up less than
9% of the state. In Louisiana, a small area of moderate drought was
present in south central parishes and was bounded on either side by
abnormally dry conditions. In Mississippi, there was a small band
of moderate drought in the southern counties that border Louisiana.
In Tennessee, conditions have improved. The easternmost counties
remained in moderate drought, whereas the southeastern counties
have improved from extreme and exceptional drought to severe
drought.

MIDWEST DROUGHT

As explained by the Midwest
Regional Climate Center, precipitation was 150 to 200 percent
of normal from southern Missouri northward through the eastern half
of Iowa, Wisconsin, northern Minnesota, and the Michigan Upper
Peninsula. In contrast, precipitation was 60 to 75 percent of
normal for the month from eastern Illinois through most of Indiana,
Ohio, and southern Lower Michigan. Areas of above normal
precipitation coincided closely with the colder areas of the
Midwest in April, and the drier areas with the warmer eastern
Midwest. The period February through April 2008 was the wettest on
record for the Midwest region, with an average 11.64 inches (29.6
cm) of precipitation. The continuation of wet weather rapidly
improved dry conditions across the Midwest, and the April 8 U.S.
Drought Monitor marked the first time since the second week of May
2005 that there was no D1 (Moderate) drought depicted in the
Midwest. April snowfall was seven times normal across much of
Minnesota, and two to three times normal across the northern half
of Wisconsin and the Michigan Upper Peninsula.

HIGH PLAINS REGION DROUGHT

As noted by the High Plains
Regional Climate Center, dryness
was present over the western two thirds of the High Plains region
for the month of April 2008. Several stations in the western part
of the region received a tenth of an inch of precipitation or less.
Drought
conditions varied from abnormally dry (D0) to extreme drought
(D3) in the region, with the D3 drought located in the western part
of North Dakota and Nebraska.

The Colorado State Climatologist's office reported a significant
number of dust storms developed this spring in southeast
Colorado.

WESTERN DROUGHT

As summarized by the Western
Regional Climate Center, precipitation
was below normal throughout the entire region. Many stations in
California and Nevada reported their driest March-April total
precipitation. Mountain snow
pack, however, remained healthy with most of the Intermountain
and Northwest areas reporting above normal snow packs on May 1st.
Only the central Sierra was below average at a dismal 56% of
normal. The Central Sierra Snow Lab, near Donner Summit, CA,
measured only 26 inches (66 cm) of snow for March and April
combined. The average is 112 inches (285 cm). Temperatures
throughout the West were below normal except for the extreme
Southwest, with some locations reporting their coolest April in
over a decade. The cool winter and its extension into spring have
significantly delayed the snow melt season, especially in the
northern half of the region, with concerns rising for late spring
flooding from the heavy mountain snow packs.

According to National Weather Service reports:

Truckee, CA had the driest March-April in the 1949-2008 period
of record

Reno, NV tied two other years for the driest March-April
(period of record goes back to 1906)

Tahoe City, CA had the second driest March-April (period of
record goes back to 1914)

NORTHEAST DROUGHT

As noted by the Northeast
Regional Climate Center, on average, the Northeast saw 90% of
its normal April precipitation. The extreme southern and northern
states saw the most precipitation this month while the centrally
located states saw the least. New York (67% of normal), New Jersey
(71% of normal) and Pennsylvania (75% of normal) were the dry
spots. Rainfall this month resulted in an improvement in drought
conditions in southeastern Maryland and southern Delaware. After
being in severe conditions for an extended period, conditions
improved to moderate by the end of April.